Optimal Anterolateral Access Corridors to the Anterior Skull Base and Paramedian Vasculature: Quantitative Analysis of Unilateral Supraorbital, Transorbital Microscopic, and Transorbital Neuroendoscopic Approaches

Objective: Transorbital neuroendoscopic surgery(TONES) has established utility but has not been compared with a similar trajectory open craniotomy, or visualization technology.

Methods: Twenty specimens underwent supraorbital craniotomy(SOC), transorbital microscopic surgery(TMS), and TONES. Morphometric analysis included length of ipsilateral cranial nerves (CN) I, CN II, optic tract, A1, and contralateral CN II; area of exposure of the frontal lobe base; and craniocaudal and mediolateral angle of attack (AOA) and volume of surgical freedom (VSF) of the paraclinoid ICA, terminal ICA, and anterior communicating artery (ACoA).

Results: All structures were accessible through an SOC. The length of the contralateral CN II and ipsilateral A1 were reachable in 25% and 15% of cases, respectively, with TMS and 35% and 15% with TONES. TMS and TONES were hindered when accessing distal vasculature ([Figs. 1]–[4]). The mean (SD) frontal lobe base parenchymal exposures for SOC, TMS, and TONES were 955.4 (261.7) mm², 846.2 (249.9) mm², and 944.7 (158.8) mm², respectively (p = 0.26). Multivariate analysis estimated that the SOC paraclinoid ICA would result in an 11.17-mm³ normalized volume (NV) increase compared with transorbital corridors (p < 0.001). TMS resulted in a 3.5-mm³ NV increase in volume compared with TONES (p = 0.04). There was no difference between the three approaches for VSF of the ipsilateral terminal ICA (p = 0.71). TMS provided increased access compared with TONES for the terminal ICA; TMS resulted in a 4.1-mm³ NV increase in VSF (p = 0.01). SOC produced the largest access corridor maneuverability to the ACoA (mean [SD] NV: 15.6 [5.6] mm³ vs. 13.7 [4.4] mm³ for TMS vs. 7.2 [3.5] mm³ for TONES (p = 0.01) and was confirmed with a 5.34-mm³ NV increase in VSF of the ACoA for SOC compared with transorbital approaches (p = 0.01).

Conclusion: Although the SOC provides superior surgical freedom for targets that require lateral maneuverability, the transorbital corridor is an option to access the frontal lobe base and terminal ICA. This study also identifies quantifiable differences in instrument freedom between the microscope and endoscope. When using the transorbital corridor, a combined visualization strategy is optimal.

Fig. 1 Percentage of surgical target structures (STSs) with SOC, TMS, and TONES approaches in which assessment of AOA and VSF was not possible.

Fig. 2 Quantitative comparison of the mediolateral and craniocaudal AOA obtained with SOC, TMS, and TONES approaches.*Statistically significant difference(p ≤ 0.05) between all three approaches by ANOVA. ^#Statistically significant difference (p ≤ 0.05) between 2 approaches by Mann–Whitney U-test. (A) Craniocaudal ipsilateral paraclinoid ICA mean (SD) AOA. SOC: 10.9° (3.3°); TMS: 7.7° (2.7°); TONES: 6.3° (2.7°). (B) Mediolateral ipsilateral paraclinoid ICA mean (SD) AOA. SOC: 26.1° (5.3°); TMS: 21.7° (5.2°); TONES: 17.7° (4.5°). (C) Craniocaudal ipsilateral terminal ICA median (IQR) AOA. SOC: 10.3° (8.4°–12.1°); TMS: 9.2° (8.6–10.3°); TONES: 7.3° (6.5–9.5°). (D) Mediolateral ipsilateral terminal ICA mean (SD) AOA. SOC: 25.4° (4.0°); TMS: 23.6° (2.4°); TONES: 21.1° (4.3°). (E) Craniocaudal ACoA mean (SD) AOA. SOC: 9.4° (2.5°); TMS: 9.0° (1.8°); TONES: 7.1° (2.7°). (F) Mediolateral ACoA mean (SD) AOA. SOC: 19.8° (4.6°); TMS: 22.5° (5.5°); TONES: 18.1° (2.5°).

Fig. 3 (A) Ipsilateral paraclinoid ICA median and IQR NV. SOC: 25.5 (13.5–28.9) mm³; TMS: 11.2 (8.4–19.0) mm³; TONES: 8.8 (6.5–10.2) mm³. (B) Ipsilateral terminal ICA median (IQR) NV. SOC: 17.1 (11.5–22.4) mm³; TMS: 15.2 (13.8–18.1) mm³; TONES: 10.5 (7.8–14.9) mm³. (C) ACoA (SD) NV. SOC: 15.6 (5.6) mm³; TMS: 13.7 (4.4) mm³; TONES: 7.2 (3.5) mm³.

Fig. 4 Illustration depicting three-dimensional modeling of the surgical corridor to the terminal ICA from SOC, TMS, and TONES approaches. (A) Anterior surgical corridor. (B) Surgical view of the cadaveric anatomy, in continuity with model parameters (SOC: VSF = 31.01 mm³, craniocaudal AOA = 16.29°, mediolateral AOA = 31.62°; TMS: VSF = 12.22 mm³, craniocaudal AOA = 8.5°, mediolateral AOA = 27.41°; TONES: VSF = 12.5 mm³, craniocaudal AOA = 6.43°, mediolateral AOA = 21.4°).

Publikationsverlauf

Artikel online veröffentlicht:
15. Februar 2022